Various techniques for fabricating microchannels in BIOMEMS devices are known in the prior art. Such techniques are described in the following patent applications: U.S. Pat. No. 6,186,660 <<Microfluidic systems incorporating varied channel dimensions>>; U.S. Pat. No. 6,180,536 <<Suspended moving channels and channel actuators for . . . >>; U.S. Pat. No. 6,174,675 <<Electrical current for controlling fluid parameters in . . . >>; U.S. Pat. No. 6,172,353 <<System and method for measuring low power signals>>; U.S. Pat. No. 6,171,865 <<Simultaneous analyte determination and reference . . . >>; U.S. Pat. No. 6,171,850 <<Integrated devices and systems for performing . . . >>; U.S. Pat. No. 6,171,067 <<Micropump>>; U.S. Pat. No. 6,170,981 <<In situ micromachined mixer for microfluidic analytical . . . >>; U.S. Pat. No. 6,167,910 <<Multi-layer microfluidic devices>>; U.S. Pat. No. 6,159,739 <<Device and method for 3-dimensional alignment of . . . >>; U.S. Pat. No. 6,156,181 <<Controlled fluid transport microfabricated polymeric . . . >>; U.S. Pat. No. 6,154,226 <<Parallel print array>>; U.S. Pat. No. 6,153,073 <<Microfluidic devices incorporating improved channel . . . >>; U.S. Pat. No. 6,150,180 <<High throughput screening assay systems in . . . >>; U.S. Pat. No. 6,150,119 <<Optimized high-throughput analytical system>>; U.S. Pat. No. 6,149,870 <<Apparatus for in situ concentration and/or dilution of . . . >>; U.S. Pat. No. 6,149,787 <<External material accession systems and methods>>; U.S. Pat. No. 6,148,508 <<Method of making a capillary for electrokinetic . . . >>; U.S. Pat. No. 6,146,103 <<Micromachined magnetohydrodynamic actuators . . . >>; U.S. Pat. No. 6,143,248 <<Capillary microvalve>>; U.S. Pat. No. 6,143,152 <<Microfabricated capillary array electrophoresis device . . . >>; U.S. Pat. No. 6,137,501 <<Addressing circuitry for microfluidic printing apparatus>>; U.S. Pat. No. 6,136,272 <<Device for rapidly joining and splitting fluid layers>>; U.S. Pat. No. 6,136,212 <<Polymer-based micromachining for microfluidic devices>>; U.S. Pat. No. 6,132,685 <<High throughput microfluidic systems and methods>>; U.S. Pat. No. 6,131,410 <<Vacuum fusion bonding of glass plates>>; U.S. Pat. No. 6,130,098 <<Moving microdroplets>>; U.S. Pat. No. 6,129,854 <<Low temperature material bonding technique>>; U.S. Pat. No. 6,129,826 <<Methods and systems for enhanced fluid transport>>; U.S. Pat. No. 6,126,765 <<Method of producing microchannel/microcavity . . . >>; U.S. Pat. No. 6,126,140 <<Monolithic bi-directional microvalve with enclosed . . . >>; U.S. Pat. No. 6,123,798 <<Methods of fabricating polymeric structures . . . >>; U.S. Pat. No. 6,120,666 <<Microfabricated device and method for multiplexed . . . >>; U.S. Pat. No. 6,118,126 <<Method for enhancing fluorescence>>; U.S. Pat. No. 6,107,044 <<Apparatus and methods for sequencing nucleic . . . >>; U.S. Pat. No. 6,106,685 <<Electrode combinations for pumping fluids>>; U.S. Pat. No. 6,103,199 <<Capillary electroflow apparatus and method>>; U.S. Pat. No. 6,100,541 <<Microfluidic devices and systems incorporating . . . >>; U.S. Pat. No. 6,096,656 <<Formation of microchannels from low-temperature . . . >>; U.S. Pat. No. 6,091,502 <<Device and method for performing spectral . . . >>; U.S. Pat. No. 6,090,251 <<Microfabricated structures for facilitating fluid . . . >>; U.S. Pat. No. 6,086,825 <<Microfabricated structures for facilitating fluid . . . >>; U.S. Pat. No. 6,086,740 <<Multiplexed microfluidic devices and systems>>; U.S. Pat. No. 6,082,140 <<Fusion bonding and alignment fixture>>; U.S. Pat. No. 6,080,295 <<Electropipettor and compensation means for . . . >>; U.S. Pat. No. 6,078,340 <<Using silver salts and reducing reagents in . . . >>; U.S. Pat. No. 6,074,827 <<Microfluidic method for nucleic acid purification and . . . >>; U.S. Pat. No. 6,074,725 <<Fabrication of microfluidic circuits by printing techniques>>; U.S. Pat. No. 6,073,482 <<Fluid flow module>>; U.S. Pat. No. 6,071,478 <<Analytical system and method>>; U.S. Pat. No. 6,068,752 <<Microfluidic devices incorporating improved channel . . . >>; U.S. Pat. No. 6,063,589 <<Devices and methods for using centripetal . . . >>; U.S. Pat. No. 6,062,261 <<Microfluldic circuit designs for performing . . . >>; U.S. Pat. No. 6,057,149 <<Microscale devices and reactions in microscale devices>>; U.S. Pat. No. 6,056,269 <<Microminiature valve having silicon diaphragm>>; U.S. Pat. No. 6,054,277 <<Integrated microchip genetic testing system>>; U.S. Pat. No. 6,048,734 <<Thermal microvalves in a fluid flow method>>; U.S. Pat. No. 6,048,498 <<Microfluidic devices and systems>>; U.S. Pat. No. 6,046,056 <<High throughput screening assay systems in . . . >>; U.S. Pat. No. 6,043,080 <<Integrated nucleic acid diagnostic device>>; U.S. Pat. No. 6,042,710 <<Methods and compositions for performing molecular>>; U.S. Pat. No. 6,042,709 <<Microfluidic sampling system and methods>>; U.S. Pat. No. 6,012,902 <<Micropump>>; U.S. Pat. No. 6,011,252 <<Method and apparatus for detecting low light levels>>; U.S. Pat. No. 6,007,775 <<Multiple analyte diffusion based chemical sensor>>; U.S. Pat. No. 6,004,515 <<Methods and apparatus for in situ concentration . . . >>; U.S. Pat. No. 6,001,231 <<Methods and systems for monitoring and controlling . . . >>; U.S. Pat. No. 5,992,820 <<Flow control in microfluidics devices by controlled . . . >>; U.S. Pat. No. 5,989,402 <<Controller/detector interfaces for microfluidic systems>>; U.S. Pat. No. 5,980,719 <<Electrohydrodynamic receptor>>; U.S. Pat. No. 5,972,710 <<Microfabricated diffusion-based chemical sensor>>; U.S. Pat. No. 5,972,187 <<Electropipettor and compensation means for . . . >>; U.S. Pat. No. 5,965,410 <<Electrical current for controlling fluid parameters in . . . >>; U.S. Pat. No. 5,965,001 <<Variable control of electroosmotic and/or . . . >>; U.S. Pat. No. 5,964,995 <<Methods and systems for enhanced fluid transport>>; U.S. Pat. No. 5,958,694 <<Apparatus and methods for sequencing nucleic acids . . . >>; U.S. Pat. No. 5,958,203 <<Electropipettor and compensation means for . . . >>; U.S. Pat. No. 5,957,579 <<Microfluidic systems incorporating varied channel . . . >>; U.S. Pat. No. 5,955,028 <<Analytical system and method>>; U.S. Pat. No. 5,948,684 <<Simultaneous analyte determination and reference . . . >>; U.S. Pat. No. 5,948,227 <<Methods and systems for performing electrophoretic . . . >>; U.S. Pat. No. 5,942,443 <<High throughput screening assay systems in . . . >>; U.S. Pat. No. 5,932,315 <<Microfluidic structure assembly with mating . . . >>; U.S. Pat. No. 5,932,100 <<Microfabricated differential extraction device and . . . >>; U.S. Pat. No. 5,922,604 <<Thin reaction chambers for containing and handling . . . >>; U.S. Pat. No. 5,922,210 <<Tangential flow planar microfabricated fluid filter and . . . >>; U.S. Pat. No. 5,885,470 <<Controlled fluid transport in microfabricated polymeric . . . >>; U.S. Pat. No. 5,882,465 <<Method of manufacturing microfluidic devices>>; U.S. Pat. No. 5,880,071 <<Electropipettor and compensation means for . . . >>; U.S. Pat. No. 5,876,675 <<Microfluidic devices and systems>>; U.S. Pat. No. 5,869,004 <<Methods and apparatus for in situ concentration . . . >>; U.S. Pat. No. 5,863,502 <<Parallel reaction cassette and associated devices>>; U.S. Pat. No. 5,856,174 <<Integrated nucleic acid diagnostic device>>; U.S. Pat. No. 5,855,801 <<IC-processed microneedles>>; U.S. Pat. No. 5,852,495 <<Fourier detection of species migrating in a . . . >>; U.S. Pat. No. 5,849,208 <<Making apparatus for conducting biochemical analyses>>; U.S. Pat. No. 5,842,787 <<(Microfluidic systems incorporating varied channel . . . >>; U.S. Pat. No. 5,800,690 <<Variable control of electroosmotic and/or . . . >>; U.S. Pat. No. 5,779,868 <<Electropipettor and compensation means for . . . >>; U.S. Pat. No. 5,755,942 <<Partitioned microelectronic device array>>; U.S. Pat. No. 5,716,852 <<Microfabricated diffusion-based chemical sensor>>; U.S. Pat. No. 5,705,018 <<Micromachined peristaltic pump>>; U.S. Pat. No. 5,699,157 <<Fourier detection of species migrating in a . . . >>; U.S. Pat. No. 5,591,139 <<IC-processed microneedles>>; and U.S. Pat. No. 5,376,252 <<Microfluidic structure and process for its manufacture>>.
The paper by L. L. Sohn, O. A. Saleh, G. R. Facer, A. J. Beavis, R. S. Allan, and D. A. Notterman, ‘Capacitance cytometry: Measuring biological cells one by one’, Proceedings of the National Academy of Sciences (USA), Vol. 97, No. 20, Sep. 26, 2000, pp. 10687-10690 discloses a polydimethylsiloxane (PDMS) biochip capable of capacitance detection of biological entities (mouse cells).
This prior art shows that passive micro-channel biochip devices are fabricated using fusion bonding of a combination of various substrates, such as: acrylonitrile-butadiene-styrene copolymer, polycarbonate, polydimethylsiloxane (PDMS), polyethylene, polymethylmethacrylate (PMMA), polymethylpentene, polypropylene, polystyrene, polysulfone, polytetrafluoroethylene (PTFE), polyurethane, polyvinylchloride (PVC), polyvinylidine fluoride (PVF). These Prior Art USA patents show that mechanical stamping or thermal forming techniques are used to define a network of micro-channels in a first substrate prior its fusion bonding to another such substrate, as to form microchannels between the two bonded substrates. The result is a simple passive micro-channel biochip device which can be patterned with conductive layers as to connect an external processor used to provoke fluid movement by electrophoresis or electroosmosis, analysis and data generation. An example of such passive micro-channel biochip devices obtained from the fusion of such polymeric substrates is shown in U.S. Pat. No. 6,167,910 <<Multi-layer microfluidic devices>>.
The Prior Art also indicates that passive micro-channel biochip devices can be fabricated from the combination of various micro-machined silica or quartz substrates. Again, assembly and fusion bonding is required. The result is again a simple passive biochip device which can be patterned with conductive layers as to connect an external processor used to provoke fluid movement by electrophoresis or electroosmosis, analysis and data generation. An example of such passive micro-channel biochip devices obtained from the fusion of such silica substrates is shown in U.S. Pat. No. 6,131,410 <<Vacuum fusion bonding of glass plates>>.
The cited US patents also indicate that passive micro-channel biochip devices can be fabricated from a passive micro-machined silicon substrate. In that case, the silicon substrate is used as a passive structural material. Again, assembly and fusion bonding of at least two sub-assemblies is required. The result is again a simple passive biochip to connect to an external processor used to provoke fluid movement, analysis and data generation. An example of such passive micro-channel biochip devices obtained from a passive micro-machined silicon substrate is shown in U.S. Pat. No. 5,705,018 <<Micromachined peristaltic pump>>.
The cited US patents also indicate that active micro-reservoir biochip devices can be fabricated from machining directly into an active silicon substrate. In that case, the control electronics integrated in the silicon substrate is used as an active on-chip fluid processor and communication device. The result is a sophisticated biochip device which can perform, into pre-defined reservoirs, various fluidics, analysis and (remote) data communication functions without the need of an external fluid processor in charge of fluid movement, analysis and data generation. An example of such active micro-reservoir biochip devices obtained from an active micro-machined silicon substrate is shown in U.S. Pat. No. 6,117,643 <<(Bioluminescent bioreporter integrated circuit>>.
These Prior Art references also indicate that passive polydimethylsiloxane (PDMS) biochips have been developed for the detection of biological entities using gold coated capacitor electrodes. FIG. 1 shows an example of such passive polydimethylsiloxane (PDMS) biochips with gold electrodes (L. L. Sohn, O. A. Saleh, G. R. Facer, A. J. Beavis, R. S. Allan, and D. A. Notterman, ‘Capacitance cytometry: Measuring biological cells one by one’, Proceedings of the National Academy of Sciences (USA), Vol. 97, No. 20, Sep. 26, 2000, pp. 10687-10690).
These Prior Art references also indicate that wax has been used to fabricate such microchannels. FIG. 2 shows that this process requires the top covers of the microchannels to be first bonded to a carrier wafer using a low temperature wax. Then, a photosensitive benzocyclobutene, BCB, is spun-on, exposed and developed as to define the sidewalls of the microchannels. Then the photodefined BCB of the carrier wafer is properly aligned and bonded to a receiving wafer integrating the bottoms of the microchannels. Then the wax of the carrier wafer is heated above its melting point as to detach the BCB bonded sidewalls and covers of the carrier wafer onto the bottoms of the receiving wafer, thus creating microchannels. An example of such an approach in shown in the paper by A. Jourdain, X. Rottenberg, G. Carchon and H. A. C. Tilmanstitled, ‘Optimization of O-Level Packaging for RF-MEMS Devices’, Transducers 2003, The 12th International Conference on Solid State Sensors, Actuators and Microsystems, Boston, Jun. 8-12, 2003, pp. 1915-1918 <<
These Prior Art references also indicate that parylene could be used to fabricate such microchannels. FIG. 3 shows that a carrier wafer could be first coated with 1.3 um of AZ1813 sacrificial photoresist over which a 0.38 um thick layer of parylene could be deposited and patterned as to expose the underlying layer of parylene. Following local etch of the exposed parylene the underlying sacrificial photoresist could be dissolved in acetone as to leave an array of free-standing parylene covers on the carrier wafer. The patterned receiving wafer integrating the sidewalls and bottoms of the microchannels could be coated with another layer of 0.38 um thick layer of parylene, could be aligned and could be pressed against the free standing pattern of parylene on the carrier wafer while heating at 230° C. under a vacuum of 1.5*10−4 Torr. The two parylene layers could polymerize together and will result in bond strength of 3.6 MPa. An example of such an approach in shown in the paper by H. S. Kim and K. Najafi, ‘Wafer Bonding Using Parylene and Wafer-Level Transfer of Free-Standing Parylene Membranes’, Transducers 2003, The 12th International Conference on Solid State Sensors, Actuators and Microsystems, Boston, June 8-12, 2003, pp. 790-793.